Chimney duct sections comprising inner and outer pipes having insulation material located in an annular passage or gap between the two pipes are known. The insulation material is rock or basalt wool having a density of about 100-200 grams/liter. The wool is packed into the annular passage via a press or manually assembled. The packing process is very slow. Hence, costs associated with the manufacture of such chimney duct sections are high. Further, since the wool is formed from very short fibers having very small diameters, environmental concerns may be associated with the duct sections.
Accordingly, there is a need for an improved chimney duct section design wherein production costs are reduced and the materials incorporated into the product are more environmentally acceptable.